Distribution: Alaska to Maine, south to California and New Mexico in the west and Illimois in eastern United states; more common west of the Cascades in Washington
Habitat: Standing or slow-moving water
Flowers: June - August
Conservation Status: Not of concern
Aquatic, herbaceous perennials from slender rhizomes, the stems sparingly branched, greenish, 1-2 mm. broad and 3-6 dm. long, the internodes only 1-3 cm. long.
Leaves alternate, submersed, the blades sessile and clasping, ovate-lanceolate to lanceolate, up to 10 cm. long and 2 cm. broad, with crisp margins, 13-to 25-veined, rounded to acute; stipules free of the leaf, 1-2 cm. long, soon shredding into numerous whitish fibers.
Flowers perfect, in 6-12 closely compact whorls, in a spike 1.5-4 cm. long, on a stout peduncle 2-10 cm. long; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.
Achenes obliquely obovate, about 3 mm. long, faintly keeled on the back, with no lateral keels, the stylar beak nearly 1 mm. long.